S C
IE N
T IF
IC H
IG H
LI G
H T
S E
N V
IR O
N M
E N
T, E
A R
T H
A N
D P
L A
N E
T A
R Y
S C
IE N
C E
S
1 4 3 I H I G H L I G H T S 2 0 2 3
PRINCIPAL PUBLICATION AND AUTHORS
Presence of uranium(V) during uranium(VI) reduction by Desulfosporosinus hippei DSM 8344T, S. Hilpmann (a), A. Rossberg (a, b), R. Steudtner (a), B. Drobot (a), R. Hübner (c), F. Bok (a), D. Prieur (a, b), S. Bauters (a, b), K.O. Kvashnina (a, b), T. Stumpf (a), A. Cherkouk (a), Sci. Total Environ. 875, 162593 (2023); https:/doi.org/10.1016/j.scitotenv.2023.162593 (a) Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology (Germany) (b) ESRF (c) Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research (Germany)
REFERENCES
[1] N. Matschiavelli et al., Environ. Sci. Technol. 53, 10514-10524 (2019). [2] A. Vatsurina et al., Int. J. Syst. Evol. Microbiol. 58, 1228-1232 (2008). [3] H. E. Roberts et al., Environ. Sci. Technol. Lett. 4, 421-426 (2017). [4] P. Wersin et al., Appl. Geochemistry 26, 931-953 (2011). [5] Z. Pan et al., Nat. Commun. 11, 1-12 (2020). [6] A. Rossberg et al., Anal. Bioanal. Chem. 376, 631-638 (2003).
are discernible. Furthermore, the U spectrum from a sample incubated for 168 h is broader than the other spectra and exhibits a shoulder on the left side of the main edge transitions. This shoulder on the low-energy side is generally associated with the formation of lower oxidation states, possibly U(IV) and/or U(V). To ascertain the precise contributions of U(IV), U(V), and U(VI), the ITFA package was employed [6], while the compounds UO2, uranyl(VI) nitrate, and UMoO5 from Pan et al. [5] were used as references for the U oxidation states +4, +6 and +5, respectively. The ITFA analysis resulted in a content of up to 10% U(IV) after an incubation time of 168 h. Furthermore, this method was used to monitor the
Fig. 117: U M4 HERFD-XANES data recorded on the cell pellets after different incubation times compared with the reference spectra of U(VI) as uranyl(VI) nitrate, U(V) as UMoO5 [5], and U(IV) as UO2. Dashed lines in (a-c) indicate the white line energy positions for U(IV), U(V), and U(VI) valence states, respectively; (d) and (e) indicate post-edge features for the uranyl(VI) structure ([U(VI)initial]. = 100 µM).
U(V) state over an extended period, up to one week, with a share of up to 30%, providing the initial evidence of the presence of U(V) in microbial U(VI) reduction by sulfate- reducing bacteria.
This study showed the presence of U(V), as examined by HERFD-XANES measurements, during U(VI) reduction by a sulfate-reducing bacterium. The results confirmed the presence of U(V) as a key intermediate for up to one week and lead to a deeper understanding of the radionuclide reduction mechanisms of sulfate-reducing bacteria, which are crucial for the final disposal of high-level radioactive waste.